Cave Divers Risk Their Lives to Explore the Underworld

For the past 14 years, photographer and filmmaker Jill Heinerth has been exploring underwater caves around the world, from lava tubes off the coast of North Africa to icebergs in the Antarctic. Wired.com recently caught up with Heinerth to talk about some of her most exciting cave diving moments, as well as the recent technological advances that have made cave diving easier, safer and more accessible to recreational divers. This gallery showcases some of Heinerth’s best underwater images and includes captions adapted from our conversation with her.

Above: “My Neighborhood Cave” in High Springs, Florida

Heinerth snapped this photo of herself as she descended through the tannic water of the Santa Fe River into her neighborhood cave in High Springs, Florida. The swirling orange blaze above her comes from the mixing of river water, stained red by decaying cypress trees, with crystal blue spring water flowing from the cave. The giant black mask she’s wearing is connected to a special diving tank called a rebreather.

“Basically, it does the same thing as a space suit,” Heinerth said. “In normal scuba gear, you’re inhaling gas and exhaling a column of bubbles into the water. But in a rebreather, you’re actually recycling your air, with carbon dioxide getting scrubbed out of the mixture and oxygen getting added back in. With an electronic rebreather, you can tune the gases that you’re using, so that in deeper water you can use helium and other gases to get the optimal mixture of breathing gas for deep water.”

Here, two divers pose in front of one of the many signs warning divers without proper training to stay out of Ginnie Springs Cave or risk their death. More than 400 people have died from cave diving accidents around the world, and most fatal accidents have involved open water divers without cave certification.

“There’s a lot of opportunity to make simple mistakes that could be fatal,” said Heinerth. “Most errors happen because of human error, although there’s been a slow progression to protect people from some of the most common mistakes through technology.” Although rebreathers can make cave diving safer by decreasing the amount of breathing gas you need to carry, Heinerth also calls rebreather tanks “the ultimate suicide machine.”

“In two minutes, I could hook it up improperly in the garage and kill myself,” she said. That’s one of the reasons why anyone who wants to buy a rebreather has to undergo mandatory safety training before receiving their unit.

In this photo, a diver swims through a palace of stalactites in Mexico’s Yucatan Peninsula. The delicate formations were created during past ice ages when the cave was dry, as rain water dripped through cracks and crevices in the limestone and left precipitated minerals behind. “An interesting aside is that our recent National Geographic project in the Bahamas included work on dating stalactite and stalagmite formations,” Heinerth said. “Some of the formations in caves can be dated back hundreds of thousands of years, and could have formed many, many sea level changes ago.”

This beautiful snapshot captures a view of the trees looking up through the clear blue water of the cave at Devil’s Eye Spring.

Plenty of cave divers enjoy exploration purely for exploration’s sake, but cave diving also gives scientists access to data that they would otherwise never be able to reach. “A cave is like a protected little underground laboratory,” said Heinerth, who has worked with scientists to do biological surveys, study new species and conduct geological studies of icebergs and lava tubes. “I even worked with an astrobiologist who was collecting algae samples from caves that are the closest roots to rudimentary life,” she said, “and I just got back from the Bahamas on an expedition where we were uncovering early human remains and early rock formations that show us a lot about ancient human history.”

Cave diving often means creeping through small spaces, like the tight passageway that these two divers are traversing in this photo.

“With cave diving, when something goes wrong you have to solve your problem right then and there with what you have,” Heinerth said. “Sometimes we swim a couple of miles underground, so that if something happens, you have to swim back a couple of miles before you can even begin to come up.”

“Buddy diving is definitely the safer way to go,” she said, “but I’m not always with somebody else. There are times, especially in exploration, where it’s small, it’s silty and another person is more of a risk than a benefit. When you’re in small spaces and you’re not able to turn around, then a second person can be a problem.”

Heinerth captured this photo of a diver swimming out of an ice cave during an expedition to study the world’s largest recorded iceberg, called B-15, which broke free from the Ross Ice Shelf in 2000. Before B-15 began cracking into pieces, it covered an area of more than 11,000 square kilometers, larger than the island of Jamaica.

“Probably the most dangerous expedition I’ve ever been on was the Antarctic project,” Heinerth said, “This particular iceberg had calved off of the ice shelf, and we went down to intercept it and find a way to get inside it.”

“On that expedition, I was almost lost at sea and also got trapped inside the iceberg. We had two separate issues — one time the entrance where we had gone in had caved and closed, and another time the current swamped us and became so strong that we couldn’t make any headway against it.”

In this photograph, the diver on the left is wearing traditional open circuit scuba gear, while the diver on the right is using a rebreather, which recycles exhaled air much like an astronaut’s space suit.

“I started diving rebreathers about 14 years ago,” Heinerth said. “I took it on really as a tool for underwater exploration. For me, it has allowed me to go deeper, stay longer, go farther in the cave and create a better safety net for image capture.” With a rebreather, Heinerth says she’s able to stay underwater for up to 12 hours, whereas with regular scuba gear, she might have only been able to stay at those depths for a few minutes. “And because it doesn’t create any bubbles,” she said, “we can flit through the environment without disturbing animals or changing the water chemistry, and you can get up close and personal with things that would otherwise be scared of bubbles.”

Here, a silhouetted diver pilots a device called the Cis-Lunar Digital Wall Mapper inside a cave at Wakulla Springs, Florida. The device, designed by aerospace engineer Bill Stone, was the first machine capable of modeling a cave in three dimensions.

“The cave project morphed into a NASA project,” Heinerth said. “It’s an autonomous, self-swimming underwater robot that can map in three dimensions and take samples. We had it down in the Antarctic during our first winter expedition, and the ultimate destination for this probe is to take it to Jupiter’s moon, Europa.”

“A lot of the technology for cave diving has crossed over from space and has been going back and forth between the two fields,” she said. “The technology is great for covering two worlds.”

The cave entrance in this photo is a window into a fresh water aquifer below. “Where I live, here in northern Florida, caves are the conduit for our drinking water,” Heinerth said. “It’s a beautiful environment.”

The diver in this photo has descended about 20 feet into the opening of Devil’s Eye Spring. Without carrying breathing gas, free divers can usually swim down only about 40 to 45 feet, but Heinerth says that a few brave souls venture further. “In Russia, I met a guy who they nicknamed ‘Aqua Man,'” she said. “In water temperature just above freezing, Aqua Man would put on a wetsuit, enter the cave, and swim a couple of hundred feet before surfacing to sip from an air pocket on the ceiling of the cave. Then he’d free dive even further in, eventually getting 300 feet into the cave with no air. He was free diving by leap-frogging from air pocket to air pocket inside the cave.”

Here, a team of Russian divers brave near-freezing temperatures to explore a cave off the coast of Siberia.

Cave diving is always challenging, but Heinerth said diving in arctic waters adds an additional element of danger. “Certainly there’s a lot of equipment preparation because of the cold, and even with the best exposure protection, there’s a very finite amount of time that you can spend in those sorts of temperatures. Nowadays people use suit heaters, and rebreathers will keep you a bit warmer, but you have to adjust your equipment to withstand the cold.”

In this photo, a diver is lowered into a drinking water well in Mexico during an archaeological expedition sponsored by the National Geographic Society.

“In the course of exploring some of the local drinking water supplies, we found skulls and paleo animal remains and pottery from different areas,” Heinerth said. “That particular well, I nicknamed the well of time, because at the very top we found rusty buckets that were just a few years old. A little deeper, we found Spanish colonial water- carrying vessels, and below that, skeletons of longhorn cattle that had been ritually placed on the mound.” As the explorers ventured further into the cave, they found older and older archaeological remains, including human skulls that had been ritually defleshed and sacrificed, and one skeleton with its hands and feet chopped off. “Probably a thief,” Heinerth said.

“We found all those things and immediately called the archives and heritage government authority in Mexico, and that’s how we launched the National Geographic project,” she said. “We were smart enough to know not to touch anything.”

In this photo, a diver checks his equipment before descending into a cave in the Canary Islands. To get to the submerged part of this cave, called a “sump,” the group had to carry their gear through more than a mile of dry passageways.

“Ten years ago, we expected (on) almost every dive for things to break and to be getting ourselves out of the cave on a wing and a prayer,” Heinerth said. “Safety and reliability have greatly increased in the past decade, and most recently a really exciting thing has happened. One of the silent killers on a rebreather is carbon dioxide, as too much carbon dioxide can cause a person to pass out and die. Now a company from the UK has designed a rebreather with an active gaseous carbon dioxide monitor — that’s a huge advance that will make the market a lot safer, and it was a pretty significant technological nut to crack.”